Voltage regulator



D 11, 1962 A. R. PERRINS ETAL 3,068,397

VOLTAGE REGULATOR Filed Jan. 14. 1960 S MMW m mg N NW 6 s 00A M M L A RV k ar Ha Aw v/ a United States Patent 3,068,397 VOLTAGE REGULATOR Allen R. Perrins, Cheshire, Walter G. Meusel and Mark W. Liberi, Bristol, Conn., assignors to The Superior Electric Company, Bristol, Conn., a corporation of Connecticut Filed Jan. 14, 1960, Ser. No. 2,476 6 Claims. (Cl. 32366) The present invention relates to an alternating current voltage regulator for automatically maintaining a substantially constant value of output voltage from a supply voltage that varies in value.

An object of the present invention is to provide an automatic voltage regulator that employs an adjustable inductive impedance for controlling the output voltage.

Another object of the present invention is to provide an automatic voltage regulator employing an adjustable inductive impedance that has a greater sensitivity in maintaining the output voltage at the selected value and which has a faster speed of response in correcting the output voltage to the desired value upon a deviation therefrom.

A further object of the present invention is to provide an automatic voltage regulator that achieves the above objects which is relatively economical to fabricate, composed of relatively few parts and is durable.

In achieving the above objects, the regulator of the present invention has input terminals normally connected to a source of AC. which may have a variable voltage and an output transformer having output terminals across which the substantially constant output voltage appears with the output voltage being less than the input voltage. Connected in series between the input treminals and the transformer is a pair of load windings of a magnetic amplifier. The windings are connected to be self-saturating by reason of their being in parallel to each other with oppositely directed one-way valve means providing unidirectional current flow in each therein. The magnetic amplifier, further, has velocity windings responsive to its rate of change, bias windings that opposite the selfsaturating of the core by the load windings and are adjusted to set the normal operating point of the magnetic amplifier and control windings, the latter providing the primary control of the impedance of the magnetic amplifier;

The value of control current in the control windings of the magnetic amplifier depends on the deviation and direction of the value of output voltage from the selected value and to sense the deviation, there is provided a sensing bridge having linear and non-linear elements that produce an AC. signal having a magnitude and a polarity indicative of the deviation. This signal is converted to a DC. signal that has a value indicative of the deviation of the R.M.S. value of the output voltage with the polarity of the signal being maintained by a ring modulator and this DC. signal is amplified by a second magnetic amplifier that is connected to be polarity sensitive. The amplified signal from the second magnetic amplifier is the control current in the first magnetic amplifier that effects the control of the output voltage.

Other features and advantages will hereinafter appear.

In the drawing, the sole FIGURE is an electrical schematic diagram of the automatic voltage regulator of the present invention.

Referring to the drawing, the automatic voltage regulator of the present invention is generally indicated by the reference numeral 10 and includes a pair of input terminals 11 and 11a and output terminals 12 and 12a having a neutral or ground 12b. The regulator hereinafter specifically disclosed provides for the output voltage to be less than the normal supply voltage of 120 "ice volts, and preferably on the order of six volts, which is a voltage that may be used for thermionic tube filament heating, the latter normally requiring a ground such as neutral 12b. Connected between the output and input terminals is an adjustable inductiveimpedance or magnetic amplifier, indicated generally by the reference numeral 13 that serves to regulate the output voltage to maintain it substantially constant. The magnetic amplifier 13 has a pair of load windings 14 connected in parallel to each other in series with the output transformer and have oppositely directed one-way valve means 15 in the parallel connection. A primary 16 of a step-down output transformer 17 is connected to the load windings and has its secondary winding connected to the output terminals '12 and 12a, with a center tap being connected to the neutral 12b.

It will be appreciated that with the above construction, current to the output terminals all flows through the load windings 14 and valve means 15 of the magnetic amplifier and in achieving the objects of the invention, the magnetic amplifier is thus connected to have its load windings produce magnetic saturating of the core thereby enabling more power to be controlled than would be possible with external feed-back windings in a same size amplifier. In order to overcome the self-saturating of the core by the load windings, there is provided a pair of bias windings 18 connected in series through a resistance 19 and a full wave rectifying bridge 20 to a winding 21 of a transformer 22 connected across the input terminals 11 and 11a. The bias windings 18 are thus energized with direct current to produce D.C. magnetization which opposes the DC. magnetization produced by the DC. current components in the load windings 14 and produce sufiicient magnetization to cause the magnetic amplifier to operate on a substantially straight portion of its characteristic curve.

Additionally wound on the core of the magnetic amplifier 13 are control windings 23 and velocity windings 24. The control windings 23 serve to primarily control the impedance of the amplifier 13 while the velocity windings aid in stabilizing the response, as will be hereinafter appreciated.

In order to provide a unidirectional current of sufficient strength in the control windings 23 which may be of one value if the output voltage is above the desired value and of a higher value if it is below the desired value, there is provided a sensing bridge 25 composed of opposite legs having identical linear resistances 26 and the other pair of opposite legs having identical nonlinear resistance 27, such as tungsten lamps. A variable resistance 28 is provided in the lead from the output terminal 12a to the bridge to enable adjusting the value of voltage across the bridge and thereby setting the value of output voltage at which the the bridge is balanced which would be the value of output voltage maintained constant.

The output signal from the bridge is through a pair of leads 29 which are connected to opposite ends of a ring modulating bridge 30. The output signal from the modulating bridge is through a pair of leads 31 and 32 which are in series with the velocity windings 24 and control windings 33 of a second magnetic amplifier, generally indicated by the reference numeral 34. The load windings 35 of the amplifier 34 are connected to the points A and A of the winding 21 of the transformer 22 and the neutral A of the windings is connected to the point A which is in a lead 36 connected to the load windings. The magnetic amplifier 34 is connected to be polarity sensitive and to be self-saturating by means of one-way valves 37 and thus it produces a DC. signal of constant polarity, the value of which is changed by the polarity and magnitude of the current in its control windings.

The lead 36 carries the DC. current from the load windings 35 through the control windings 23 to the center tap A while a condenser 38 filters the current and serves as a decoupler.

With the above construction it would be appreciated that the core of the magnetic amplifier 13 is magnetized toward saturation in one direction by the load windings 14 while the bias windings 18 oppose the saturation of the load windings 14 to unsaturate the core in its operating range and the control windings 23 thereby control the saturation in the operating range so that with the output voltage being at the desired value, the core operates at a point in its substantially linear range of operation.

'If the output voltage decreases below the desired value caused by a decrease in the input voltage or an increase in the load then the magnetic amplifier 13 will become more saturated by an increase of the current in its control windings, decreasing the impedance of the magnetic amplifier which causes the output voltage to return to the desired value. Conversely if the output voltage is too high the degree of saturation of the magnetic amplifier is decreased by a decrease of the current in the control windings, increasing its impedance and hence lowering the output voltage.

In order to provide a reference voltage for the ring modulator 30, there is a secondary winding 39 on transformer 22 which has one end connected to the neutral 12b and its other end to the center of a pair of identical resistors 40 and 41. With the output voltage being at the desired value, the voltage across the leads 31 and 32 which effect the saturation of the magnetic amplifier 34 about its quiescent position, has no voltage thereacross by reason of the identical current flowing through the oneway valves 30a and 30c to the other side of the winding 39. Even though the reference voltage is alternating current, a change in polarity of the reference voltage will not cause a voltage to appear across the leads 31 and 32 by reason of the resistors 40 and 41 being identical. Hence -there is no current flow in the magnetic amplifier control windings 33 when the output voltage is at its desired value. It will be appreciated that with no current in the control windings 33, the magnetic amplifier 34 is partially self-saturated by the one-way valves 37 and has a quiescent current flowing through its load windings.

If the output voltage rises above a pre-selected value, then there will be a voltage signal from the bridge 25 across the leads 29 which will be in phase and of the same polarity as the A.C. reference voltage. The voltage across the leads 29 is modulated by the ring modulator 30 and appears as a direct current having a value equal to approximately the signal voltage across the leads 31 and-32 and with the increase in voltage the lead 32 will be plus with respect to the lead 31 causing current flow in 6 velocity feed-back windings 24 and the control windlugs 33 of the magnetic amplifier. This current will decrease the saturation of the core of the magnetic amplifier 34; decreasing the current in the control windings 23 which in turn will increase the impedance of the magnetic amplifier 13 thereby decreasing the output voltage to the desired value.

Conversely with the output voltage being smaller than the desired value, a signal voltage will appear across the leads 29 which will be in phase with the reference signal but of opposite polarity, and this after passage through the modulator will appear as a voltage between the leads 31 and 32 with the lead 31 being positive with respect to the lead 32. This voltage causes current to flow through the velocity windings 24 and the control windings 33, the latter resulting in an increase in saturation of the core of the magnetic amplifier 34 which increases the control current through the windings 23, decreasing the impedance of the magnetic amplifier 13 and effecting an increase in the output voltage to the desired value.

The velocity windings 24 by being connected in series with the control windings 33 of the m g amplifier 34 but between the windings and the resistors 40 and 41 will have the same current that flows through the control windings as a result of the signal voltage appearing in the leads 31 and 32. However, the velocity feed-back windings produce a voltage that is in opposition to the voltage across the resistors 40 and 41 and its value is dependent upon the direction of change and the rate of change of the magnetism in the core of the magnetic amplifier 13. Thus, with no voltage across the resistors 40 and 41, no voltage is produced in the velocity feedback windings and whenever a signal does appear across the resistors 40 and 41, it is opposed by the voltage induced in the velocity feed-back windings when the magnetization of the core of the amplifier 13 starts to change. The velocity feed-back windings thereby provide stability of the regulator.

The regulator of the present invention employs the ring modulating bridge to rectify the low level signals from the sensing bridge without introducing distortion into the signal and yet maintain its polarity sense. Furthermore, the reference voltage employed in the modulating bridge is taken from the winding 39 connected to the input which prevents the introduction of any distortion into the reference voltage which may occur if the latter were taken from the output terminals of the regulator.

It will be clear that the intermediate output voltage of the regulator in the present embodiment of the invention is approximately 6.3 volts, and to provide the desired sensitivity small deviations therefrom must be sensed and then be corrected. In order to prevent any loss of value of the deviation, the sensing bridge is connected to the output terminals and the signal therefrom by the ring modulator is rectified to provide an R.M.S. value of the deviation which is the signal that controls the second magnetic amplifier 34.

it will accordingly be appreciated that there has been disclosed an automatic voltage regulator which employs an adjustable impedance inductive device to regulate the output voltage to maintain it substantially constant with variations in the input voltage. The regulator has a fast speed of response and increased sensitivity by use of a magnetic amplifier which is self-saturating as the adjustable inductive impedance device and the employment of a second magnetic amplifier that is self-saturatingly polarized to amplify the control signal for the first mag netic amplifier. Moreover, by the use of a ring modulating bridge a control signal for the second amplifier is produced that is indicative of the R.M.S. value of the deviation of the output voltage from the pre-selected value with little loss of the signal from the sensing bridge.

Variations and modifications may be made within the scope of the claims and portions of the improvements may be used without others.

We claim:

1. An A.C. automatic voltage regulator comprising input terminals, output terminals, regulating means connected to input and output terminals for regulating the voltage and including a variable inductive impedance means having at least two load windings and a control winding with means connecting the load windings in parallel to each other and including one-way valves to cause unidirectional current to flow in the load windings for producing a self-saturating magnetization of the impedance means, a sensing bridge for sensing the deviation of the output voltage from a selected value and producing an A. C. signal indicative of the direction and magnitude of the deviation of the output voltage therefrom, a source of reference voltage, a ring modulating bridge connected to receive the signal from the sensing bridge and the reference voltage to produce a DC. signal indicative of the direction and magnitude of the deviation, and amplifier means connected to receive the DC signal from the modulating bridge to amplify the signal and to impress the amplified signal on the control winding to vary the impedance of the impedance means to adjust the output voltage to the selected value.

2. An automatic voltage regulator comprising input terminals, output terminals, regulating means connected to input and output terminals and including a magnetic amplifier having at least two load windings, a control winding and a velocity feedback winding, means connecting the load windings in parallel to each other and including one-way valves to cause unidirectional current to flow in the load windings for producing a self-saturating magnetization of the magnetic amplifier, a sensing means for sensing the deviation of the output voltage from a selected value and producing a signal indicative of the direction and magnitude or" the deviation of the output voltage therefrom, amplifier means connected between the sensing means and the control windings to amplify the signal to vary the impedance of the magnetic amplifier to adjust the output voltage to the selected value, and means connecting the velocity feed-back winding in series between the sensing means and the amplifier means, said velocity feed-back windings producing a signal which opposes the signal from the sensing means when the magnetic amplifier is changing its impedance.

3. An automatic voltage regulator comprising input terminals, output terminals, regulating means connected to input and output terminals and including a magnetic amplifier having at least two load windings and a control winding, means connecting the load windings in parallel to each other and including one-way valves to cause unidirectional current to flow in the load windings for producing a self-saturating magnetization of the magnetic amplifier, a sensing bridge for sensing the deviation of the output voltage from a selected value and producing an A.C. signal indicative of the direction and magnitude of the deviation of the output voltage therefrom, a source of reference voltage, a ring modulating bridge connected to receive the signal from the sensing bridge and the reference voltage to produce a DC. signal indicative of the direction and magnitude of the deviation, a second magnetic amplifier having load windings and control windings connected between the sensing means and the control windings of the first magnetic amplifier to amplify the signal and to impress the amplified signal on the control windings to vary the impedance of the first magnetic amplifier to adjust the output voltage to the selected value, said second magnetic amplifier having means including one-way valves for connecting the load windings thereof together to cause polarized self-saturating magnetization and connections connecting its control windings to receive the signal from the sensing means.

4. An automatic voltage regulator comprising input terminals, output terminals, regulating means connected to input and output terminals and including a magnetic amplifier having at least two load windings, control windings, and velocity feed-back windings, means connecting the load windings in parallel to each other and including one-way valves to cause unidirectional current to flow in the load windings for producing a self-saturating magnetization of the magnetic amplifier, a sensing bridge for sensing the deviation of the output voltage from a selected value and producing an A.C. signal indicative of the direction and magntiude of the deviation of the output voltage therefrom, a source of reference voltage, a ring modulating bridge connected to receive the signal from the sensing bridge and the reference voltage to produce a DC. signal indicative of the direction and magnitude of the deviation, a second magnetic amplifier having load windings and control windings connected between the sensing means and the control windings of the first magnetic amplifier to amplify the signal and to impress the amplified signal on the control windings to vary the impedance of the first magnetic amplifier to adjust the out put voltage to the selected value, said second magnetic amplifier having means including one-way valves for connecting the load windings thereof together to cause polarized self-saturating magnetization and connections connecting its control windings to receive the signal from the sensing means, and means connecting the velocity feedback winding in series between the sensing means and the amplifier means, said velocity feed-back windings producing a signal which opposes the signal from the sensing means when the magnetic amplifier is changing its impedance.

5. The invention as defined in claim 3 in which the source of reference voltage includes means connected adjacent the input terminals to obtain the voltage therefrom.

6. An A.C. automatic voltage regulator comprising input terminals, a step down transformer having a primary winding and a secondary winding having a neutral tap and with output terminals connected to the ends of the secondary winding, a variable inductive impedance means having at least two load windings and a control winding, means connecting the load windings in parallel to each other and in series between the input and primary winding of the transformer including one-way valves to cause unidirectional current to flow in the load windings for producing a self-saturating magnetization of the impedance means, a sensing bridge connected to the secondary winding for sensing the deviation of the output voltage from a selected value and producing an A.C. signal indicative of the direction and magnitude of the deviation of the output voltage therefrom, a source of reference voltage, a ring modulating bridge connected to receive the signal from the sensing bridge and the reference voltage to produce a DC. signal indicative of the direction and magnitude of the deviation, and including a connection to the center tap of the secondary winding, and amplifier means connected to receive the D.C. signal from the modulating bridge to amplify the signal and to impress the amplified signal on the control windings to vary the impedance of the impedance means to adjust the output voltage to the selected value.

References Cited in the file of this patent UNITED STATES PATENTS 2,825,864 Eagen Mar. 4, 1958 

